Velocity dispersion around ellipticals in MOND

TL;DR

This paper compares how different gravitational models, including Newtonian with dark matter and MOND, explain the observed velocity dispersion around elliptical galaxies on small and large scales, finding MOND fits both well.

Contribution

It demonstrates that MOND can successfully fit velocity dispersion data around ellipticals on multiple scales, unlike standard Newtonian models with or without dark matter.

Findings

MOND fits observed velocity dispersions on both small and large scales.

Standard CDM models struggle with small-scale velocity dispersion.

Pure baryonic Newtonian models have difficulties on large scales.

Abstract

We investigate how different models that have been proposed for solving the dark matter problem can fit the velocity dispersion observed around elliptical galaxies, on either a small scale (~ 20kpc) with stellar tracers, such as planetary nebulae, or large scale (~ 200kpc) with satellite galaxies as tracers. Predictions of Newtonian gravity, either containing pure baryonic matter, or embedded in massive cold dark matter (CDM) haloes, are compared with predictions of the modified gravity of MOND. The standard CDM model has problems on a small scale, and the Newtonian pure baryonic model has difficulties on a large scale, while a fit with MOND is possible on both scales.